Means to control magnetic circulation in electric-current-producing devices.



MEANS T0 CONTROL MAGNETIC CIRCULATION IN ELECTRIC CURRENT PRODUCING DEVICES.

APPLICATION FILED OUT. 1, 1910.

Patented Nov. 19, 1912.

, NIT D STATES PATENT- OFFICE.

EDWARD F. SMITH, OF CINCINNATI, OHIO, ASSIGNOR TO THE SMITH ELECTRIC .TOQL

(30., OF CINCINNATI, OHIO, A-CORPORATION OF OHIO.

MEANS To CONTROL MAGNETIC CIRCULATION IN ELECTRIC-CURRENT-PRODUCING DEVICES.

do declare the following to be a clear, full,

and exact description ofthe invention, at-

tention being'called .to the drawing which accompanies this application and forms a part thereof. 7

As is well known in an electric motor, operated by a dynamo-current there is also generated an electro-Inotive force which counteracts the incoming dynamo-current whereby the motor is operated. The voltage of this counter electro-motive force is directly proportional to-the density of the magnetic field through which the armature of the motor rotates, or as it may also be stated, to the number of lines of force containedinthe magnetic circulation which prevails between complementary poles. It

is also known that the yoltage of this counter-electromotive force and the consequent speed of the armature may be controlled and regulated .by control and regulation of theintensity of volume of this magnetic This condition may be taken advantage of for the purpose ofregulatlng the speed of motorsused toloper'ate-tools as for instancedrills and grinders directly connected to the armature shaft and" my invention relates to certain new and useful means whereby in a motor so used the magnetic circulation is regulated andcontrolled for "the purpose of regulating and controlling correspondingly the capacity of the motor to generate this counter electro-m'otive 'force and in consequence thereof the rotary speed of its armature, which is influenced by said magnetic circulation.

In the following specification and particularly pointed out in the claims at the end thereof, will be found a full description of my invention, together with its operation, parts and construction, which latter is also illustrated in the accompanying drawing, in which Figure 1, shows in cross-section a motorhousing, constructed for use in connection with a tool to be electrically operated, the

Specification of Letters Patent. Application filed October 1, 1910. Serial No. 584,810.

Patented No v. 19, 1912.

housing being provided with the speed-controlling means-contemplated by-my inventlon. F 2, in a similar View shows these means in a different position; Fig. 3,shows in a similar View my intention applied to a inultipolar motor. Fig. 4,shows a portion of such a motor-housing enlarged and illus- 'trates a certain feature of constructionof my device.

In the drawing, A indicates the motorhous ng formed by an annular, hollow castmg, and B indicates field-magnet-cores forming PIOJGCtlOYiS onthe inner side of said housing and of which there may be one or more. The heavy dotted lines shown across said cores are intended to represent the wire-coils of the field-inagnets, or the space occupied by said coils.

C indicates. the .armature mounted on shaft 6-.

Ordinarily, magnetic circulation proceeds as indicated by the arrows shown in connection with the light dotted lines in Fig. 1, p'assingfrom one pole 6 across and through the rotary path of'the armature, to another pole and through part of the housing between said poles, said part of the housing consti tuting the yoke between the poles, and being indicated by letter -a. nine of this magnetic circulation depends on. the size or capacity of the conduit whichfaf- Obviously the 'volfords passage for it /and is represented by the site or'area of the yoke taken in a plane transversely to the direction in which the magnetic currents move- Consequently, by changing the size of this area within certain limits, the volume of the magnetic flux .or the lines of force available for co-action with the. armature are proportionately affected, which effect necessarily extends to the current-producing capacity of the motor and to the speed of" its armature. The means whereby I attain these effects are constructed as follows: The thickness of at least ,one of those parts of the housing where it forms a yoke, and by preference the thickness of all these yoke-forming parts is reduced to form recesses cl as 'shownin all the figures of the drawing, said recesses be- .ing elongated and provided on the inside of the yoke parallel to the axis housing and armature and may extend through the entire length of the same. Into each of these recesses I fit a complementaryyoke-section trol as shown in Figs. 1 to 3 by diverting the .up as shown by the dotted lines in Fig. 2.

I), which is adjustably supported so that it 1 may occupy a normal position in which it i is entirely within said recesses as shown in 1 Figs. 1 and at and completes with the adjacent and contiguous parts of the yoke the normal and largest cross-sectional area ofthe same available to carry magnetic circulation. From this position it. may be adjusted to a position shown in Fig. 2, in which itforms no part of this cross-sectional area of the yoke and whereby the area available to carry magnetic flux is lim ited to the reduced part of the yoke, this being the reduced thickness of the metal of the housing remaining outside of the deepest part of the recesscss Means are provided to move yoke-sections D to positions intermediate these two extreme positions and each of which positions affects the rotation of the armature to a proportionate degree. I

In Figs. 1, 2, 3, and 4, recess (1 is substan tially semi-circular and the yoke-section is correspondingly shaped. "Inthis case this latter may be supported by trunnion-joinnals 10, which [ind hearings in opposite ends of the housing. An arm 11 is pr yided, it may connect to one of the trunnions, or to section. D direct, in which latter case it reaches the same through a slot in the housing. By means of this arm, sect-ion D may be moved to various positions, each providing accordingly different changes of speed in the armature. Means to positively hold the adjustable yoke sections in adjusted positions may be dispensed with, since the magnetic attraction is suiiicient for this purpose. -Where a number of yoke-sections are provided as shown in Fig. 3, these arms 11 may all be connected for simultaneous manipulation'as for instance by a ring 12, suitably mounted.

' While as shown, the magnetic-circuit is controlled by the adjustment of the size of the area of its conduit, I amplify this conmagnetic circuit from its normal passage through the rotary path of the armature.

iary member (yoke-section D) into thespace between two complementary poles whereby this projected part, for the time being, forms an auxiliary and additional pole as best shown in Fig. 2, whereby the magnetic circuit is shunted out of its normal ath and short circuited, a substitute circuit being set The manipulation for adjusting the position of yoke-section D, may be a positive one in either direction, or it may be positive in one direction only and automatic for the purpose of returning it to its normal position. In the latter case a spring 14: of proper strength is used to return-the yokesections to normal condition, it maybe ar-' ranged as shown in. Fig. 4 where it occu pies a. recess between the yoke and the yokesection, one end of it being connected to the yoke and the other to the yoke-section. In this case, as soon the switch which con-- trols the feet circuit to the motor is turned ofi', consequent cessation of the magnetic attraction which held the yoke-section in ad justed p0sition, 'enables the spring to return the yoke-section to normal position, which means normal speed conditions of the armature. Accidents are thus avoided, as'for instance when the motoris started up with parts left in a position previouslyadjusted 'for a certain speed and which speed for a tool about to be connected would be unsuited. The features of the invention are likewise applicable to generators or dynamos.

I am aware that complementary yoke sections have been used in connection with yokes and where these sections are fitted to occupy a space between the opposite ends or a completely divided housing, I consider such a construction objectionable inasmuch as it reduces the structural strength of the housing and complicates the construction and fitting thereof. "It will be noted that in myconstruction this objection is absent and rigidity of the structure is preserved. by an integral yoke-portion, the objectof the invention being atttained by merely reducing the thickness of the metal of this yoke portion. I am also aware that such current-control has been attempted by means provided on the outside of the motor-housing and occupying recesses in the magnetcores. This construction is objectionable for the reason that it is difiicult to move the de- ,vices, to be moved for adjustment, out of their normal positions, because such move ment is resisted by the magnetic attraction which is highest at the particular point where these devices are'located in the recesses of the cores. It is furthermore objectionable because available only where the width of the magnet-cores is sutiiciently large to permit recessing It cannot be readily used on cylindrical cores and not at all when such cylindrical cores areof small diameter like on some arc-light machines. It is entirely excluded where cores are built up of laminae or plates, which is generally the case now on large motors, since there the recesses would'cut out the bolts whereby said plates are held together. It is also more dilficult to support or attach such a motor-housing recessed on its outside, it also takes up more room, by reason of these devices located on the outside of it and the outwardly open recesses are exposed to dust and grit.

Having described my invention, I claim as new: 4 v

'1. In means for controlling the magnet circulation in, a" 'motor constructed to be adapted for operation of a tool, the combination of an annular housing containing part between these complementary poles is reduced in thickness to form an elongated Irecess parallel to the axis of the housing and openon the inner s de thereof, a cone plementary yoke-section fitted to this recess and means to adjust the position of this section, to graduate the area of the yoke through which the magnetic circuit passes. 2. In means for Controlling the magnetic Circulation in a motor constructed to he adapted for operation of a tool, the CO11iliination of'an annular housing containing complementary poles and part of which housing constitutes-a yoke through which the magnetic circulation passes and which part between these complementary poles is reduced in thickness to form an elongated recess parallel to. the axis of the housing and open on the inner side thereof, a complementary yoke-section fitted to this recess and means to adjust the position of this section so that it is either entirely within said recess or only in part so whereby the area. of the yoke through which the magnetic circuit passes is accordingly modified. 3. In means for controlling the magnetic circulation in a motor constructed to he i adapted for operation of a tool, the combination of an annular housing containing fieldmagnet cores adapted to constitute complementary magnetic poles, and a. yoke-member supported adjustably on the housing be tween complementary poles and in a man 4:. In means for controlling the magnetic circulation in a motor constructed to be adapted for operation of a tool, the combination of an annular housing containing lield-magnet cores adapted to constitue complementary magnetic poles and part of which housing between these cores constitrues a yoke through which the magnetic circulation passes and which part on the inside of the housing is reduced in thickness to form an elongated recess between these poles and parallel to th'eaxis, of the housing, acoinplementary housing-section titted to this recess and means to adjust the position of this section to supplementor to reduce the area of that part o'tthe housing and. to also cause said section to project into the space between complclncntarypoles, to attract the magnetic circuit from its normal path and to up a slnint-circulation between. it and one of the poles.

In means for controlling the magnetic circulation in a motor constructed to be adapted for operation of a tool, the combination of an annular lunising, part of which constitutes a yoke through which the magnetic circulation passes and which part is reduced in thickness to form an elongated recess parallel to the axis of the housing, a complementary yoke-section fitted to this recess and adapted to entirely close the same, means to adjust'the position of this section to graduate the area of the yoke through which the magnetic circuit passes and means to-return this yoke-section automatically to its normal position.

In testimony whereof, I hereunto ail i my signature in the presence of two witnesses.

Witnesses C. SPnNenL, T. IJEBEAU. 

